1. Field of the Invention
The present invention relates to an optical recording medium in which at least one of the recording, reproducing and recording-once of information is performed by irradiating a light to a recording material comprising a dye which has a high solubility in an organic solvent and is excellent in light-resistance, stability during the preservation and recording properties, thereby causing an optical change, such as a change in transmittance or reflectance in a recording material, and, method and apparatus for the optical recording and reproducing.
2. Description of the Related Art
Recently, the development of DVD±R is proceeding. For improving the recording capacity, it is necessary to develop a recording material for the microminiaturization of the recording pit, a technique for the image compression which is represented by Moving Picture Experts Group-2 (MPEG2) and a technique for lowering the wavelength of a semi-conductor laser used for reading the recording pit.
Up until now, as a semi-conductor laser, only a barcode reader and a diode for an AlGaInP laser having a wavelength of 670 nm which is used for a measuring instrument have been commercialized; however, accompanying with rendering an optical disc to have a high-density, a red laser has started to be used in full-scale in the optical storage market.
In the case of DVD drive, the light source is standardized by two wavelengths, such as 635 nm and 660 nm for a laser diode. On the other hand, DVD-ROM drive for Read Only is commercialized with a wavelength of 650 nm. In such a situation, the most preferred DVD±R medium is a medium in which the recording and reproducing can be performed with a light having a wavelength of from 630 to 700 nm.
As a dye used for a DVD±R optical recording medium, a dye which is excellent in recording properties, light-resistance and stability during the preservation is desired.
Recently, as a dye for a recording material, the development of a dye, such as a polymetine dye, an azo-metal-chlate dye, a cyanine dye, a squarylium dye and other complex compound dyes, is proceeding.
The cyanine dye and the squarylium dye are excellent in optical properties and have satisfactory signal properties; however, the above-noted dyes have poor light-resistance, so that almost of them are not practicable, when they are used individually as a dye for the optical recording medium. For improving the above-noted poor light-resistance of an optical recording medium produced using the above-noted dyes, the development of a light stabilizer used in combination with the dyes is proceeding; however, there are a few combinations of a dye and a light stabilizer which can obtain both the function of light stabilizing and satisfactory signal properties.
On the other hand, a formazan-metal chlate dye among the above-noted azo-metal chlate dyes is known as a dye having extremely high light stability and an application thereof as a material for the optical recording is attempted in many times (see Japanese Patent (JP-B) Nos. 2791944 and 3456621; Japanese Patent Application Laid-Open (JP-A) Nos. 08-295079, 09-95520, 09-193546, 10-337958, 10-151862, 10-151863, 10-152623 and 10-154350; International Publication No. WO 00/75111 and JP-A Nos. 2001-23235, 2002-11950, 2002-11953, 2002-274033, 2002-283722, 2002-293027 and 2003-145939).
In nearly all of the above-noted cases of attempts to apply the formazan-metal chlate dye as a material for the optical recording, a wavelength of a light absorbed by the dye was too large, so that it was difficult to satisfy all of signal qualities and recording qualities as the optical recording medium.
Therefore, an optical recording medium in which the recording, reproducing and additional recording of information can be performed by irradiating a light to a recording material comprising a dye which has a high solubility in an organic solvent and is excellent in light-resistance, stability during the preservation and recording properties, thereby causing an optical change, such as a change in transmittance or reflectance in a recording material has not been attained and a swift attainment thereof is nowadays desired.